Field of the Invention
This invention relates to a micro-pump ant a method for the production thereof. More particularly, it relates to a micro-pump serving as a drive source for allowing mechanical motions of a work module body or a micro-machine and various actuators, sensors, etc. operating with module functions or a micro-pump for controlling the flow of an extremely small amount of fluid and to a method for the production of the micro-pump.
Description of the Prior Art
In recent years, diligent researches have been devoted to developing micro-machines to be used in the medical field and in various industrial fields. Functionally, micro-machines are machines of varying functions used generally in industrial fields such as nipping and lifting work module body and objects or fixing and moving various sensors. They have extremely small overall sizes falling approximately in the range of from 0.1 to 10 mm. They are not produced simply by miniaturizing various existing machines.
For the purpose of enabling micro-machines of this nature to produce a practical operation, drive sources of high reliability are indispensable. Numerous operating principles have been proposed for these micro-machines. They are intended to allow mechanical motions of the work module body or a micro-machine and various actuators, sensors, etc. operating with module functions. Depending on the kind of work, they are required to permit flow of fluids such as gas, water, and chemical solutions to suites of work. Further, they are possibly compelled to fix machine bodies or work units firmly in place in certain work environments.
A review of such drive sources prevailing over a wide range of industrial fields reveals the fact that a great many of them make use of jacks and lifts which operate hydraulically. The reason for their popular use is that they are able to generate a large Dower with a relatively simple construction and they are durable and reliable. Particularly in situations where speed does not account for much but reliable supply of a large drive force is an essential requirement, methods which utilize the pressure of a fluid are effective. When the use of a fluid in this manner is contemplated as a drive source for a micro-machine, the drive source requires a pump which discharges and aspirates the fluid.
Among the conventional micro-pumps whose operations have found popular approval to date is that which is disclosed in the artiste titled "Journal of the Institute of Electronics, Information and Communications Engineers (IEICE) C Vol. J71-C, No. 12, pp. 1705-1711 (Dec. 1988).
This micro-pump 101 is manufactured by the application of the micro-machining technique. As illustrated in FIG. 11, it comprises a pump body having joined face to face a silicon substrate 103a forming two check valves 102a and 102b and a silicon substrate 103b forming a pressure chamber 104, a movable diaphragm 105, and a mesa 106 and a laminated piezo actuator 107 (2 mm.times.3 mm.times.9 mm) fixed on the Mesa 106 of the pump body. A voltage signal 108 applied to the actuator 107 causes the actuator 107 to generate a force which gives a push to the mesa 106 and deforms the diaphragm 105. At this time, the cheek valve 102a is shut and the cheek valve 102b is opened to introduce the fluid through an inlet 109 and discharge it through an outlet 110.
In terms of the operating principle, the conventional micro-pump described above is a positive-displacement type diaphragm pump which is one of the types of general-purpose industry grade pumps. It approximately measures 10 mm.times.10 mm.times.8 mm. Thus, it is hardly proper to conclude that this conventional micro-pump realizes an ideal micro-pump which is expected to possess a cross-sectional area in the range of from 1 to 5 mm.sup.2 and an overall size of about 1 mm.times.2 mm.times.4 mm to suit use with a micro-machine.
When the operating principle of the general-purpose industrial pump is directly applied to the micro-pump, the miniaturization of the mechanical part thereof entails the problem of proportionally increasing the viscous drag of the fluid and the frictional resistance of the sliding parts. The drive source which is sufficiently small in volume and is capable of generating a force large enough to drive (deform) a diaphragm yet remains to be developed.
An object of this invention, therefore, is to provide an extremely small micro-pump which has an overall size of about 1 mm.times.2 mm.times.4 mm and can be advantageously used as a drive source for operating a micro-machine and permitting effective flow of the fluid for the micro-machine and a method for the production of the micro-pump.